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An Urban Experience
Antimicrobials and the skin microbiome
The most common isolates associated with bacterial folliculitis in dogs are Staphylococcus spp. During
 are states of cAD, commonly with bacterial folliculitis (super cial pyoderma), there is decreased microbial diversity, with S. pseudintermedius and S. schleiferi overrepresented. A similar progression has been documented in human AD with increased abundance of S. aureus and S. epidermitis. Following culture-directed systemic antimicrobial therapy for pyoderma with cAD, one study showed microbial diversity is restored, with
a decreased levels of Staphylococcus present (Figure 1). However, the recurrence of pyoderma in some dogs four to six weeks following treatment is accompanied by reduction in diversity (Figure 2).
A recent study documented that topical antibiotic treatment provided a longer lasting impact on the microbiota compared to relatively minor changes
by topical antiseptics. Triple antibiotic ointment was shown to have a greater impact than mupirocin in
overall microbiota disruption. The impact of commensal bacteria on maintaining health and barrier function of
the skin is an important consideration, though we know relatively little about their role. Both coagulase negative and coagulase positive/variable Staphylococcus are common constituents of the skin microbiota. Host adapted coagulase negative commensals can alter the colonizing ability of coagulase positive Staphylococcus (S. aureus in humans and mice). This study showed
that treatment with topical antibiotics can be disruptive
to Staphylococcal populations, with a greater effect on those with a higher baseline level of Staphylococcus. This disruption can promote exogenous association/potential colonization by the potential pathogen S. aureus.
There is still much to be learned from study of the skin microbiome, and the  eld is rapidly evolving. Baseline communities may be predictive in therapeutic responses, and competition amongst microbial communities can avail different therapeutic avenues. As processing
and analytics progress, the diagnostic potential of auditing these communities is tremendous. In an era
of antimicrobial resistance, consideration of the entire host’s microbiota is crucial when treating a patient as disruption of the microbiota will be both local (e.g. skin) and systemic.
References and Further Reading
1. Bradley CW, Morris DO, Rankin SC, Cain CL, Misic AM, Houser T, et al. Longitudinal Evaluation of the Skin Microbiome and Association with Microenvironment and Treatment in Canine Atopic Dermatitis. J Invest Dermatol. 2016;136(6):1182-90.
2. Grice EA, Kong HH, Conlan S, Deming CB, Davis J, Young AC, et al. Topographical and temporal diversity of the human skin microbiome. Science. 2009;324(5931):1190-2.
3. Kong HH, Oh J, Deming C, Conlan S, Grice EA, Beatson MA, et al. Temporal shifts in the skin microbiome associated with disease  ares and treatment in children with atopic dermatitis. Genome Res. 2012;22(5):850-9.
4. Meisel JS, Hannigan GD, Tyldsley AS, SanMiguel AJ, Hodkinson BP, Zheng Q, et al. Skin Microbiome Surveys Are Strongly In uenced by Experimental Design. J Invest Dermatol. 2016;136(5):947-56.
5. Misic AM, Davis MF, Tyldsley AS, Hodkinson BP, Tolomeo P, Hu B, et al. The shared microbiota of humans and companion animals as evaluated from Staphylococcus carriage sites. Microbiome. 2015;3:2.
6. Rodrigues Hoffmann A, Patterson AP, Diesel A, Lawhon SD, Ly HJ, Elkins Stephenson C, et al. The skin microbiome in healthy and allergic dogs. PLoS One. 2014;9(1):e83197.
7. SanMiguel AJ, Meisel JS, Horwinski J, Zheng Q, Grice EA. Topical antimicrobial treatments can elicit shifts to resident skin bacterial communities and reduce colonization by Staphylococcus aureus competitors. Antimicrob Agents Chemother. 2017.
8. Song SJ, Lauber C, Costello EK, Lozupone CA, Humphrey G, Berg-Lyons D, et al. Cohabiting family members share microbiota with one another and with their dogs. Elife. 2013;2:e00458.
9. Torres S, Clayton JB, Danzeisen JL, Ward T, Huang H, Knights D, et al. Diverse bacterial communities exist on canine skin and are impacted by cohabitation and time. PeerJ. 2017;5:e3075.

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